Skin immunosenescence: decreased receptor for activated C kinase-1 expression correlates with defective tumour necrosis factor-α production in epidermal cells

Summary Background Skin immunosenescence accounts for increased susceptibility in the elderly to cutaneous infections and malignancies, and decreased contact hypersensitivity and response to vaccination. We have recently shown in immune cells that decreased expression of the receptor for activated C kinase (RACK)‐1 underlies defective protein kinase C (PKC) activation and functional immune impairment with ageing. Objectives This study was designed to determine if an age‐related decline in skin RACK‐1 expression was present and whether it correlated with defective tumour necrosis factor (TNF)‐α production. Methods PKC isoforms and RACK‐1 expression were evaluated by Western blot analysis and by immunofluorescence in skin obtained from Sprague‐Dawley rats of different ages. TNF‐α release by epidermal cells induced by lipopolysaccharide, 12‐O‐tetradecanoyl‐phorbol‐13‐acetate and the contact allergen dinitrochlorobenzene was assessed by the L929 biological assay. Results Skin obtained from old rats (> 18 months) showed decreased RACK‐1 immunoreactivity if compared with young rats (